Our provision for income taxes and the related effective income tax rates are as follows (in millions):



	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2019		2018		2019		2018

Provision for income taxes	$	(71)	$	(133)	$	(271)	$	(383)
Effective tax rate		17.4%		17.5%		22.6%		33.1%

For the three months ended September 30, 2019, the effective income tax rate differed from the United States (“U.S.”) statutory rate of 21% primarily due to an increase in the estimated impact of base erosion and anti-deferral tax (“BEAT”) offset by the return to provision true-up of the U.S. Federal 2018 tax return filed in October 2019, primarily due to tax reform.

For the nine months ended September 30, 2019, the effective income tax rate differed from the U.S. statutory rate of 21% primarily due to an increase in the estimated impact of BEAT offset by return to provision true-up of the U.S. Federal 2018 tax return filed in October 2019, primarily due to tax reform, additional net tax expense of $86 million driven by changes to our tax reserves and the release of foreign valuation allowances on deferred tax assets.

For the three months ended September 30, 2018, the effective income tax rate differed from the U.S. statutory rate of 21% primarily due to additional tax amounts related to the estimated annual impact of Global Intangible Low-Taxed Income (“GILTI”) and BEAT offset by benefits related to Foreign Derived Intangible Tax (“FDII”) and a $48 million benefit related to an adjustment to the provisional estimate of the one-time Toll Charge recorded in 2017.

For the nine months ended September 30, 2018, the effective income tax rate differed from the U.S. statutory rate of 21% primarily due to additional tax expense of $172 million related to a preliminary agreement with the Internal Revenue Service (“IRS”) to settle the income tax audits for the years 2013 and 2014, additional tax amounts related to the estimated annual impact of GILTI and BEAT, offset by benefits related to FDII, $28 million from the release of a foreign valuation allowance on deferred tax assets that are now considered realizable and a $48 million benefit related to an adjustment to the provisional estimate of the one-time Toll Charge recorded in 2017.